U.S. patent number 5,886,173 [Application Number 08/903,121] was granted by the patent office on 1999-03-23 for metallation of macrocycles with 2,4-dicarbonyl-metal complexes.
This patent grant is currently assigned to Pharmacyclics, Inc.. Invention is credited to Gregory W. Hemmi, Miguel Rosingana.
United States Patent |
5,886,173 |
Hemmi , et al. |
March 23, 1999 |
Metallation of macrocycles with 2,4-dicarbonyl-metal complexes
Abstract
A method has been developed which utilizes a
metal-2,4-dicarbonyl complex as an organic solvent soluble metal
ion source in the metallation of polyazamacrocycles including
porphyrins, expanded porphyrins and porphyrinoid compounds. Use of
a metal ion source which is soluble in the metallation reaction
medium produces significantly higher yields of a measurably purer
product than is achieved using an insoluble or only sparingly
soluble metal salt as in the prior art. Additionally, because the
metallation can be performed in relatively concentrated mixtures,
the reaction times are dramatically shorter and the amount of waste
produced is less than when simple metal salts serve as the metal
ion source. Further, use of the soluble metal-2,4-dicarbonyl
complex simplifies the purification protocol required for the
metallated expanded porphyrin.
Inventors: |
Hemmi; Gregory W. (Sunnyvale,
CA), Rosingana; Miguel (San Francisco, CA) |
Assignee: |
Pharmacyclics, Inc. (Sunnyvale,
CA)
|
Family
ID: |
25416978 |
Appl.
No.: |
08/903,121 |
Filed: |
July 30, 1997 |
Current U.S.
Class: |
540/472; 540/145;
534/11; 534/15; 540/465 |
Current CPC
Class: |
C07D
487/22 (20130101); A61K 49/06 (20130101) |
Current International
Class: |
A61K
49/06 (20060101); C07D 487/22 (20060101); C07D
487/00 (20060101); C07D 487/22 (); C07D
257/00 () |
Field of
Search: |
;534/11,15
;540/145,472,465 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
RG. Lauffer Magn. Reson Q. (1990) 6: 2. .
C.F. Meares et al. Br. J. Cancer Suppl. (1990) 10: 21. .
G. Jori et al. J. Photochem. Photobiol. B (1990) 6: 93. .
S.W. Young et al. Proc. Nat. Acad. Sci. U.S.A. (1996) 93: 6610.
.
S.W. Young et al. Invest. Radiol. (1996) 31: 280. .
J.L. Sessler et al. Accounts of Chemical Research (1994) 27: 43.
.
S.W. Young et al. Invest. Radiol. (1996) ??L 353. .
J.F. Desreux Lanthanide Probes in Life, Chemical and Earth
Sciences. Theory and Practice, Bunzli, J.--C.G. Ed., Elsevier, New
York (1989) pp. 43-64..
|
Primary Examiner: Shah; Mukund J.
Assistant Examiner: Sripada; Pavanaram K
Attorney, Agent or Firm: Townsend and Townsend and Crew
Claims
What is claimed is:
1. A process for metallating an expanded porphyrin in an organic
solvent, comprising:
(a) contacting a metal salt with a 2,4-dicarbonyl compound to form
a metal-2,4-dicarbonyl complex between said 2,4-dicarbonyl compound
and a metal ion derived from said metal salt; and
(b) reacting said metal-2,4-dicarbonyl complex with said expanded
porphyrin in said organic solvent to form a metallated expanded
porphyrin.
2. A process in accordance with claim 1 in which said expanded
porphyrin is a member selected from the group consisting of
texaphyrins and texaphyrin precursors.
3. A process in accordance with claim 1 in which said
2,4-dicarbonyl compound and said metal salt are contacted in a
molar ratio of from about 3.5:1.0 to about 0.1:1.0.
4. A process in accordance with claim 1 in which said
2,4-dicarbonyl compound and said metal salt are contacted in a
molar ratio of from about 1.5:1.0 to about 0.5:1.0.
5. A process in accordance with claim 1 in which said metal salt
comprises a lanthanide ion.
6. A process in accordance with claim 5 in which said lanthanide
ion is a member selected from the group consisting of lutetium
(III), dysprosium(III), and gadolinium (III).
7. A process in accordance with claim 1 in which said 2,4-carbonyl
compound has the formula: ##STR5## wherein: R.sup.21 is a member
selected from the group consisting of heterocycles, hydroxy,
alkoxy, amino, alkylamino, C.sub.1 -C.sub.6 alkyl and C.sub.1
-C.sub.6 alkyl substituted with one or more substituents
independently selected from the group consisting of heterocycles,
hydroxy, alkoxy, amino, alkylamino, carboxy, cyano and halogen;
R.sup.22 is selected from the group consisting of H and C.sub.1
-C.sub.6 alkyl; and
R.sup.23 is a member selected from the group consisting of
heterocycles, hydroxy, alkoxy, amino, alkylamino, C.sub.1 -C.sub.6
alkyl and C.sub.1 -C.sub.6 alkyl substituted with one or more
substituents independently selected from the group consisting of
heterocycles, hydroxy, alkoxy, amino, alkylamino, carboxy, cyano
and halogen.
8. A process in accordance with claim 7 in which:
R.sup.21 is a member selected from the group consisting of
heterocycles, hydroxy, alkoxy, amino, alkylamino, C.sub.1 -C.sub.3
alkyl and C.sub.1 -C.sub.3 alkyl substituted with one or more
substituents independently selected from the group consisting of
heterocycles, hydroxy, alkoxy, amino, alkylamino, carboxy, cyano
and halogen;
R.sup.22 is H; and
R.sup.23 is a member selected from the group consisting of
heterocycles, hydroxy, alkoxy, amino, alkylamino, C.sub.1 -C.sub.3
alkyl and C.sub.1 -C.sub.3 alkyl substituted with one or more
substituents independently selected from the group consisting of
heterocycles, hydroxy, alkoxy, amino, alkylamino, carboxy, cyano
and halogen.
9. A process in accordance with claim 7 in which;
R.sup.21 is a member selected from the group consisting of is a
member selected from the group consisting of heterocycles, hydroxy,
alkoxy, amino, alkylamino, methyl and methyl substituted with one
or more substituents independently selected from the group
consisting of heterocycles, hydroxy, alkoxy, amino, alkylamino,
carboxy, cyano and halogen;
R.sup.22 is H; and
R.sup.23 is a member selected from the group consisting of is a
member selected from the group consisting of heterocycles, hydroxy,
alkoxy, amino, alkylamino, methyl and methyl substituted with one
or more substituents independently selected from the group
consisting of heterocycles, hydroxy, alkoxy, amino, alkylamino,
carboxy, cyano and halogen.
10. A process for metallating a texaphyrin precursor in an organic
solvent, comprising:
(a) contacting a metal salt with a 2,4-dicarbonyl compound to form
a metal-2,4-dicarbonyl complex between said 2,4-dicarbonyl compound
and a metal ion derived from said metal salt; and
(b) reacting said metal-2,4-dicarbonyl complex with said texaphyrin
precursor in said organic solvent to give a metallated texaphyrin
precursor; and
(c) oxidizing said texaphyrin precursor to a texaphyrin-metal
complex.
11. A process in accordance with claim 10 in which said
2,4-dicarbonyl compound is a 2,4-diketone.
12. A process in accordance with claim 10 in which said organic
solvent is a polar organic solvent.
13. A process in accordance with claim 10 in which said organic
solvent is a C.sub.1 -C.sub.4 alcohol.
14. A process in accordance with claim 10 in which said metal salt
is a member selected from the group consisting of salts of
yttrium(III), dysprosium(III), lutetium (III) and
gadolinium(III).
15. A process in accordance with claim 10 in which said metal salts
comprise an anion selected from the group consisting of acetate,
chloride, nitrate, oxide and sulfate.
16. A process in accordance with claim 10 in which said
texaphyrin-metal complex is: ##STR6## in which: each of R.sup.1
through R.sup.4 and R.sup.6 through R.sup.9 is independently a
member selected from the group consisting of hydrogen, halide other
than iodide, hydroxyl, alkyl, alkoxy, oligo(alkoxy), aryl, nitro,
formyl, acyl, saccharyl, and alkyl, alkoxy, and oligo(alkoxy)
substituted with one or more of the following substituents: halo
other than iodo, hydroxy, amino, carboxy, and carbamoyl;
R.sup.5, R.sup.10, R.sup.11 and R.sup.12 are each independently a
member selected from the group consisting of hydrogen, alkyl,
alkoxy, oligo(alkoxy), aryl, and alkyl, alkoxy, or oligo(alkoxy)
substituted with one or more of the following substituents:
hydroxy, amino, carboxy, and carbamoyl;
M is a member selected from the group consisting of monovalent,
divalent and trivalent metal ions; and
n is zero, 1 or 2.
17. A process in accordance with claim 16 in which:
R.sup.1 is hydroxyalkyl; R.sup.2, R.sup.3 and R.sup.4 are
alkyl;
R.sup.5, R.sup.6, R.sup.9, R.sup.10, R.sup.11 and R.sup.12 are
hydrogen atoms;
R.sup.7 and R.sup.8 are independently a member selected from the
group consisting of hydrogen, hydroxyalkyl, carboxyalkyl,
carboxyalkoxy, hydroxyalkoxy, alkoxy and oligo(alkoxy);
M is a member selected from the group consisting of chromium (III),
manganese (II), manganese (III), iron (II), iron (III), cobalt
(II), nickel (II), copper (II), indium (III), praseodymium (III),
neodymium (III), samarium (III), gadolinium (III), terbium (III),
dysprosium (III), holmium (III), europium (II), europium (III),
erbium (III), lutetium (III), ytterbium (III), yttrium (III),
cerium (III), thulium (III) and lanthanum (III); and
n is 1 or 2.
18. A process in accordance with claim 16 in which:
R.sup.7 and R.sup.8 are independently a member selected from the
group consisting of hydrogen, carboxyalkoxy, hydroxyalkoxy, alkoxy
and oligo(alkoxy);
M is a member selected from the group consisting of yttrium (III),
gadolinium (III), terbium (III), dysprosium (III), europium (II),
europium (III), erbium (III), and lutetium (III); and
n is 1 or 2.
19. A process in accordance with claim 18 in which:
M is a member selected from the group consisting of gadolinium
(III) and lutetium (III); and
n is 2.
20. A process in accordance with claim 10 in which said
texaphyrin-metal complex is: ##STR7##
Description
FIELD OF THE INVENTION
This invention relates to the metallation of macrocyclic ligands,
particularly porphyrinoid macrocycles such as texaphyrins, in
organic solvents using organic soluble 2,4-dicarbonyl complexes of
metal ions.
BACKGROUND OF THE INVENTION
Polyazamacrocyclic metal complexing agents such as the
polyazamacrocycles (e.g., 1,4,7,10-tetraazacyclododecane and its
derivatives, "TACD"), porphyrins (e.g., tetraphenylporphine, "TPP")
and porphyrinoid compounds are of interest as both therapeutic and
diagnostic agents. For example, derivatives of TACD complexed with
paramagnetic metal ions have been used as contrast enhancing agents
for magnetic resonance imaging (MRI) to enhance the diagnostic
yield of images obtained with this technique. See, for example,
Lauffer, R. B., Magn. Reson. Q. 1990:6, 2 and references therein.
Metallated tetraazamacrocycles have also been used therapeutically
and are particularly useful in cancer chemotherapy. See, for
example, Meares, C. F., et al., Br. J. Cancer Suppl. 1990:10,
21.
Metalloporphyrins are of interest as photosensitizing agents for
tumor therapy. See, for example, Jori, G., et al., J. Photochem.
Photobiol. B 1990:6, 93. Additionally, porphyrins which are
metallated with paramagnetic metal ions such as gadolinium (III)
have been used as MRI contrast enhancing agents. For example, see
Lyon, R. C., et al., Magn. Reson. Med. 1987:4, 255. The gadolinium
complexes of a class of porphyrinoids or expanded porphyrins known
as "texaphyrins" have proven of particular interest in imaging
applications. For example, see, Young, S. W., et al., Proc. Nat.
Acad. Sci. U.S.A. 1996:93, 6610 and Young, S. W., et al., Invest.
Radiol. 1996:31, 280. In addition, the lutetium (III) complexes of
texaphyrins are useful in photodynamic therapy applications.
Woodburn, K. W., et al., J. Clin. Laser Med. Surg. 1996:14, 343;
Young, S. W., et al., Photochem. Photobiol. 1996:63, 892.
The texaphyrins are aromatic pentadentate macrocyclic "expanded
porphyrins" that are useful as magnetic resonance imaging (MRI)
contrast agents, radiosensitizers, chemosensitizers and as agents
in photodynamic therapy (PDT). As used herein, the term "expanded
porphyrins" denotes a tripyrrolic pentaazaporphyrinoid compound. A
texaphyrin is an aromatic benzannulene containing both 18.pi.- and
22.pi.-electron delocalization pathways. See, for example, Sessler,
J. L., et al., Accounts of Chemical Research 1994:27, 43.
Texaphyrins and water-soluble texaphyrins and methods of
preparation have been described in U.S. Pat. Nos. 4,935,498,
5,252,720, 5,256,399, 5,272,142, 5,292,414 and 5,599,923, all of
which are incorporated herein by reference.
The metal complexes of aromatic texaphyrins are produced by the
oxidation and metallation of a reduced nonaromatic macrocycle
precursor (the "sp.sup.3 " compound). The resulting reaction
mixture contains free (uncomplexed) metal ions in solution together
with the texaphyrin-metal complex product. The free metal ions must
be removed from the reaction mixture because they can have a
deleterious effect on biolocalization (reducing efficacy) or on
stability, and they can interfere with use of the texaphyrin-metal
complex in any of its various functions. More importantly, the free
metal ion can render texaphyrin-metal complex preparations toxic in
vivo.
In current practice, texaphyrins are metallated using a mixture of
the macrocycle and a metal salt in an organic solvent such as
methanol. When the metal salt is only sparingly soluble in the
organic solvent, the metallation reaction is slow, the
rate-limiting step being the dissolution of the metal salt. To
offset the low solubility of the metal salt, it is necessary to use
substantial volumes of the organic reaction solvent, a
stoichiometric excess of the metal salt and long reaction times. As
the reaction is scaled up, large amounts of both solvent and metal
salt are required. This quickly passes from unwieldy to
impractical. As the required amounts of solvent and metal salt
increase, there is a need for specialized reaction vessels, the
amount of chemical waste generated is increased, and purification
of the metallated macrocycle becomes burdensome.
Production of large volumes of waste to produce relatively small
amounts of product is undesirable due to both the expense of the
starting chemicals and the expense associated with disposing of the
chemical waste. Further, there is a growing sensitivity to the
long-term environmental impact associated with disposal of chemical
waste in landfills or by incineration. Thus, both economic and
ecological concerns dictate that the amount of waste chemicals
produced by a reaction sequence be minimized whenever possible.
The current reaction sequence affords yields of the desired
macrocycle-metal complex which are low, often no more than 20-30%
of the theoretical yield. Further, the required reaction times are
lengthy (e.g., 29 h). Purification protocols must be used to remove
from the reaction mixture the sparingly soluble unreacted metal
salt, which is present in substantial excess, thereby increasing
the time and number of steps required to isolate the desired
product. Thus, a method for metallating expanded porphyrins, such
as texaphyrins, which affords good yields of the desired product,
after a short reaction time and a simple purification protocol
would be quite desirable. If such a method could also reduce
solvent and metal salt use it would constitute a substantial
advance in this field. This invention provides such a method.
SUMMARY OF THE INVENTION
It has now been discovered that an intermediate
metal-2,4-dicarbonyl complex which is soluble in an organic solvent
can be used to metallate macrocyclic ligands. The intermediate
2,4-dicarbonyl complex is formed by the reaction between a metal
ion derived from a metal salt and a 2,4-dicarbonyl compound. Once
formed, the intermediate metal-2,4-dicarbonyl complex is reacted
with the macrocyclic ligand in an organic solvent. Because the
metal-2,4-dicarbonyl complex has a greater solubility in organic
solvents than the precursor metal salt, it is possible to conduct
the metallation of the macrocycle at higher concentrations than is
possible with the uncomplexed metal salt, thus reducing solvent
use. The enhanced solubility of the metal ion source and the
increased concentration of reactants result in shorter reaction
times than are necessary when the uncomplexed metal salt is used as
the metal ion source. Additionally, yields of the desired
metal-macrocycle which are substantially improved over those of the
prior art can be achieved using the method of the instant
invention.
An additional advantage which emerges out of the use of an
organic-soluble metal ion source is that the metallated macrocycle
can be considerably easier to isolate from the reaction mixture.
For example, in the synthesis of a Lu(III)-texaphyrin complex using
a Lu(III)-acetylacetonate in methanol, the complex formed between
Lu(III) and the 2,4-diketone (2,4-pentanedione) is soluble in
acetone, yet the Lu(III)-texaphyrin complex is acetone-insoluble.
Thus, unreacted Lu(III)-acetylacetonate is quickly and easily
separated from the desired product by washing the insoluble
Lu(III)-texaphyrin with acetone. The simplicity of this method
stands in contrast to those of the prior art which required
contacting a solution of the crude product with a zeolite capable
of entrapping the unreacted Lu(III) ion. At least two zeolite
treatment cycles were required to obtain satisfactory removal of
uncomplexed Lu(III). The zeolite treatments were time-consuming,
requiring a period of stirring followed by filtration to remove the
zeolite. Through the use of an organic-soluble metal ion source,
the present invention avoids these difficulties.
Thus, in a first aspect, the invention provides a process for
metallating an expanded porphyrin in an organic solvent,
comprising:
(a) contacting a metal salt with a 2,4-dicarbonyl compound to form
a metal-2,4-dicarbonyl complex between the 2,4-dicarbonyl compound
and a metal ion derived from the metal salt; and
(b) reacting the metal-2,4-dicarbonyl complex with the expanded
porphyrin in the organic solvent to form a metallated expanded
porphyrin.
The discovery extends to metal ions in general. Furthermore, the
organic solvent may be any of a range of polar solvents. The metal
salt to be used as a source of the metal ion can be selected such
that the metal salt itself has low solubility in the organic
solvent prior to complexation by the 2,4-dicarbonyl. The
complexation permits the solubilization of the metal ion salt and
affords access to metallated expanded porphyrins which cannot be
synthesized in good yields using prior art methods.
Although the discovery extends to expanded porphyrins in general
and also to metal ions in general, it is of particular interest as
applied to texaphyrins and metal ions.
Thus, in a second aspect, the invention provides a process for
metallating a texaphyrin precursor in an organic solvent,
comprising:
(a) contacting a metal salt with a 2,4-dicarbonyl compound to form
a metal-2,4-dicarbonyl complex between the 2,4-dicarbonyl compound
and a metal ion derived from the metal salt; and
(b) reacting the metal-2,4-dicarbonyl complex with the texaphyrin
precursor in the organic solvent to give a metallated texaphyrin
precursor.
In preferred embodiments of the above-described aspects of the
invention, the metal-2,4-dicarbonyl complex is formed between a
trivalent lanthanide ion and 2,4-pentanedione. In particularly
preferred embodiments, the lanthanide ion is lutetium (III) or
Gd(III) and the metallation of the expanded porphyrin is conducted
in a C.sub.1 -C.sub.4 alcohol such as methanol.
The characteristics and advantages of each of the aspects and
embodiments of the invention will become apparent from the
description that follows.
DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS
Macrocyclic metal ion complexing agents are known in the art and
have found use as both diagnostic and therapeutic agents. Complexes
between metal ions and macrocyclic ligands are used as MRI contrast
agents, radiosensitizers, and as agents in PDT, radioimmunotherapy
and other medical applications. Although the discussion below
focuses on the texaphyrins as a representative example of a metal
ion complexing expanded porphyrin, those of skill in the art will
recognize that the present invention is broadly applicable to metal
ion complexing expanded porphyrins in general. The use of
texaphyrins as a representative example is intended neither to
define nor limit the invention.
Texaphyrins and other expanded porphyrins, both prior to
complexation and as metal complexes, are known in the art. Formula
I is a representative generic formula for the sp.sup.3 precursors
to the texaphyrins: ##STR1## In one aspect of the invention, the
sp.sup.3 texaphyrin precursor is metallated using a
metal-2,4-dicarbonyl complex. In preferred embodiments of this
aspect of the invention, the texaphyrin precursor is oxidatively
metallated using a metal-2,4-dicarbonyl complex. Oxidation can be
effected by molecular oxygen, chemical oxidants or electrochemical
methods.
Formula II is a representative generic formula for metal complexes
(metallotexaphyrins) formed by metallation and oxidation of the
expanded porphyrins of Formula I: ##STR2## In these formulas: each
of R.sup.1 through R.sup.4 and R.sup.6 through R.sup.9 is
independently a hydrogen atom, halide other than iodide, hydroxyl,
alkyl, alkoxy, oligo(alkoxy), aryl, nitro, formyl, acyl, or
saccharyl; or alkyl, alkoxy, or oligo(alkoxy) substituted with one
or more of the following substituents: halo other than iodo,
hydroxy, amino, carboxy, or carbamoyl;
R.sup.5, R.sup.10, R.sup.11 and R .sup.12 are each independently a
hydrogen atom, alkyl, alkoxy, oligo(alkoxy), or aryl; or alkyl,
alkoxy, or oligo(alkoxy) substituted with one or more of the
following substituents: hydroxy, amino, carboxy (--CO.sub.2 H), or
carbamoyl (--C(O)NH.sub.2);
M is a monovalent, divalent or trivalent metal ion; and the formal
charge "n" of the metallotexaphyrin is correspondingly zero, 1 or
2. Further charges may be introduced by ionized portions of any of
the R-groups.
The terms used herein are defmed as follows:
"Alkyl" denotes straight-chain, branched-chain, saturated and
unsaturated groups. "Alkoxy" denotes "alkyl" with an added oxygen
atom covalently linking the alkyl group to the remainder of the
formula. Straight-chain, saturated groups are preferred for both
alkyl and alkoxy. Further preferred alkyl and alkoxy groups are
those containing 1 to 10 carbon atoms, with 1 to 5 carbon atoms per
group particularly preferred.
"Oligo(alkoxy)" denotes 2 to 12 alkoxy groups covalently linked in
either a linear or a branched configuration. Linear oligo(alkoxy)
moieties have a structure such as --O--(CH.sub.2).sub.m
--O--(CH.sub.2).sub.m --O--(CH.sub.2).sub.m --... --O--C.sub.m
H.sub.2m+1, where "m" is an integer, the same or different along
the length of the chain. Branched moieties have two or more
--O--(CH.sub.t).sub.m --groups are bonded to a common third
--O--(CH.sub.t).sub.m --group, where "t" has a value which is
independently selected from 0,1 and 2 for each (CH.sub.t).sub.m
group. Linear configurations are preferred. Chains of 2 to 6 alkoxy
groups (--O--(CH.sub.2).sub.m --) are preferred. The individual
alkoxy groups may be the same or different, and individual alkoxy
groups preferably contain from 1 to 6 carbon atoms each, and most
preferably from 1 to 3 carbon atoms each.
"Aryl" denotes groups formed from the six-carbon ring of benzene or
the condensed six-carbon rings of other aromatic derivatives.
Examples are phenyl, naphthyl, anthryl and phenanthryl. The
preferred aryl group is phenyl.
"Acyl" denotes organic acid groups lacking the OH of the carboxyl
group. Preferred acyl groups are those containing 2 to 12 carbon
atoms, preferably 2 to 8, and most preferably 2 to 4. Examples are
acetyl, propionyl, butyryl, and benzoyl.
"Saccharyl" denotes monosaccharides and other carbohydrate groups
that can be either synthesized from or hydrolyzed to
monosaccharides, the groups being formed by the elimination of the
hydrogen atom bonded either to an oxygen atom or a carbon atom.
Included within the term "saccharyl" are radicals of
monosaccharides, disaccharides, and oligosaccharides, as well as
open-chain forms of these groups and various derivatized forms.
Examples are radicals formed from hexoses such as D-glucose,
D-mannose, and D-galactose; pentoses such as D-ribose and
D-arabinose, ketoses such as D-ribulose and D-fructose;
disaccharides such as sucrose, lactose and maltose; derivatives
such as acetals, amines and phosphorylated sugars, examples of
amines being galactosamine, glucosamine, sialic acid and
D-glucamine derivatives such as 1-amino-1-deoxysorbitol.
"Heterocyclic" is used herein to describe a saturated, aromatic or
unsaturated non-aromatic group having a single ring or multiple
condensed rings from 1-12 carbon atoms and from 1-4 heteroatoms
selected from nitrogen, sulfur or oxygen within one or more of the
rings. Such heterocycles are, for example, tetrahydrofuran,
morpholine, piperidine, pyrrolidine, thiophene, pyridine,
isoxazole, phthalimide, pyrazole, indole, furan, or benzo-fused
analogues of these rings. Also encompassed within the term
"heterocyclic" are substituted heterocycles.
"Halogen" is used herein to refer to fluorine, bromine, chlorine
and iodine atoms.
"Hydroxy" is used herein to refer to the group --OH.
"Amino" is used to describe primary amines, --NH.sub.2.
"Carboxy" denotes the group --COO(H), in either its acidic or
anionic form.
"Cyano" is used to describe the group --CN, wherein the bond
between carbon and nitrogen is a triple-bond.
"Alkylamino" denotes secondary and tertiary amines of the general
formula --NR.sub.1 R.sub.2 wherein one of R.sub.1 and R.sub.2 is
hydrogen and the other is an alkyl group or R.sub.1 and R.sub.2 are
the same or different alkyl groups.
"Independently" signifies that two or more of the groups
immediately preceding the term are either identical or different,
i.e., selection of one from the list following the term does not
affect selection of the other(s).
"Substituted" encompasses both single and multiple substitutions,
the latter including multiple substitutions by the same substituent
as well as mixtures of different substituents.
In further preferred embodiments of the invention, R.sup.1 is alkyl
or hydroxyalkyl; R.sup.2, R.sup.3 and R.sup.4 are alkyl; R.sup.5,
R.sup.6, R.sup.9, R.sup.10, R.sup.11 and R.sup.12 are hydrogen
atoms; R.sup.7 and R.sup.8 are independently a hydrogen atom,
hydroxyalkyl, carboxyalkyl, carboxyalkoxy, hydroxyalkoxy, alkoxy or
oligo(alkoxy). In still further preferred embodiments, R.sup.7 and
R.sup.8 are independently a hydrogen atom, hydroxyalkoxy,
carboxyalkoxy, alkoxy, or oligo(alkoxy).
The methods described herein are not limited to use with
texaphyrins. These methods can be practiced with a variety of
different macrocyclic compounds including, for example, natural and
synthetic porphyrins, expanded porphyrins and
polyazamacrocycles.
The metals represented by M include both paramagnetic and
diamagnetic metals, the former being particularly useful for
complexes used as MRI contrast agents, and the latter being
particularly useful in photodynamic therapy. The use of either of
these classes of metal ions is not intended to be limited by this
generalization. Preferred metals are generally those having atomic
numbers of 21-30 (inclusive), 39, 48, 49, 57-71 (inclusive,
lanthanides), and 90-103 (inclusive, actinic), with oxidation
states of 2 or 3. Of these, the ones having atomic numbers of 25,
48, 49, 39 or 57-71 (inclusive) are more preferred. Examples of
such metals are chromium (III), manganese (II), manganese (III),
iron (II), iron (III), cobalt (II), nickel (II), copper (II),
indium (III), praseodymium (III), neodymium (III), samarium (III),
gadolinium (III), terbium (III), dysprosium (III), holmium (III),
europium (II), europium (III), erbium (III), lutetium (III),
ytterbium (III), yttrium (III), cerium (III), thulium (III) and
lanthanum (III).
In a still more preferred embodiment, the metal ion is yttrium
(III) or a lanthanide ion. In an even more preferred embodiment,
the metal ion is a lanthanide ion. Of the lanthanide ions,
gadolinium (III), dysprosium (III) and lutetium (III) are the most
preferred.
Examples of specific compounds that are presently preferred are
those in which M is Gd(III), Y(III), Lu(III), Eu(III) or Dy(III);
R.sup.1 is 3-hydroxypropyl; R.sup.2 and R.sup.3 are ethyl; R.sup.4
is methyl; R.sup.5, R.sup.6, R.sup.9, R.sup.10, R.sup.11, and
R.sup.12 are hydrogen; and R.sup.7 and R.sup.8 are both
--O(CH.sub.2).sub.3 OH or --O(CH.sub.2 CH.sub.2 O).sub.3 CH.sub.3,
or R.sup.7 is hydrogen, CH.sub.3 or OCH.sub.3 and R.sup.8 is
--O(CH.sub.2 CH.sub.2 O).sub.3 CH.sub.3 or --O(CH.sub.2).sub.n COOH
where n is 1-3.
A wide variety of 2,4-dicarbonyl compounds can be used as the
complexing agent for the metal ion in practicing this invention.
Currently, a non-uniform nomenclature exists in the art for such
2,4-dicarbonyl compounds. For example, 2,4-diketones corresponding
in structure to Formula III are named as 1,3-diketones, or
alternatively, as 2,4-diketones. The scope of the invention is not
intended to be limited by this aberration in the nomenclature and
the only structural limitation placed on the 2,4-dicarbonyl
compounds of use in the invention is that there be at least one
carbon with at least one ionizable hydrogen atom located in a
position between the two carbonyl functionalities. The method of
this invention can be practiced with any 2,4-dicarbonyl
incorporating the general structural motif shown in Formula (III).
##STR3##
In Formula III, R.sup.21, R.sup.22 and R.sup.23 are independently
chosen and can be, for example, hydrogen, alkyl, substituted alkyl,
aryl, acyl, heterocyclic, alkoxy, cyano, hydroxy, halide or amino
groups. When the radical is a substituted alkyl group, the
substituents are independently chosen from, for example,
heterocycles, hydroxy, alkoxy, amino, alkylamino, carboxy, cyano
and halogen. Also encompassed within the structure of Formula III
are derivatives wherein either or both R.sup.21 and R.sup.23 are
oxygen which bears a negative charge (i.e., the carbonyl moiety is
a carboxylate) and which is associated with a positively charged
counterion comprising a metal ion (e.g., Li.sup.+, Na.sup.+,
K.sup.+, Ca.sup.+2, Ba.sup.+2).
In a preferred embodiment of the invention R.sup.21 and R.sup.23
are C.sub.1 -C.sub.6 alkyl groups or C.sub.1 -C.sub.6 substituted
alkyl groups and R.sup.22 is H or an alkyl group. In a more
preferred embodiment, R.sup.21 and R.sup.23 are C.sub.1 -C.sub.3
alkyl groups and R.sup.22 is H. In a still more preferred
embodiment R.sup.21 and R.sup.23 are either unsubstituted or
substituted methyl groups and R.sup.22 is H.
The use of derivatives of 2,4-dicarboxylic acids such as, for
example, malonic acid are within the scope of the instant
invention. Thus, the 2,4-dicarbonyl compound can comprise diesters
such as dimethyl- or diethyl-malonate, diamides such as malonamide,
or dialdehydes such as malonaldehyde. Additional examples of
2,4-dicarbonyl compounds include, but are not limited to
1,3-acetonedicarboxylic acid, N-(acetoacetyl)glycine,
o-acetoacetoluidide, acetoacetamide, acetoacetanilide,
o-acetoacetanisidide, acetoacetic acid and ethyl acetoacetate. The
above list is intended merely to offer examples of 2,4-dicarbonyl
compounds of use in practicing the instant invention and is not
intended to serve as a limitation on the range or identity of
compounds of use in conjunction with this invention. Additional
dicarbonyls which form organic solvent-soluble complexes with metal
ions, and with lanthanides in particular will be apparent to those
of skill in the art.
In certain preferred embodiments, the 2,4-dicarbonyl compound is a
2,4-diketone. 2,4-diketones of use in practicing the instant
invention include, but are not limited to, acetylacetone,
trifluoroacetylacetone, hexafluoroacetylacetone,
thenoyltrifluoroacetone, 2,2,6,6-tetramethylheptane-3,5-dione,
1,1,1,5,5,6,6,7,7,7-decafluoro-2,4-heptanedione, 4,6-dioxoheptanoic
acid, 3-ethyl-2,4-pentanedione and 5-methyl-1,3-hexanedione.
Additionally, 2,4-diketones in which one of the hydrogens on the
carbon between the two carbonyl groups is replaced with an alkyl
(e.g. 2-methyl-1,3-hexanedione) or substituted alkyl can be used in
the method of the invention. Ketones having more than 2 carbonyl
groups within their framework such as
1-(3-(2,4-dioxopentyl)phenyl)pentane-2,4-dione (a tetraketone) and
cyclic ketones such as 1,3-cyclohexanedione can also be used to
practice the invention. In further preferred embodiments the
2,4-diketone is 2,4-pentanedione or a derivative thereof.
The appropriate 2,4-dicarbonyl compound in any particular case will
be one that combines with the metal ion to form a complex that is
substantially soluble in the solvent used for the expanded
porphyrin metallation reaction. By "substantially soluble" is meant
that the metal-2,4-dicarbonyl complex is sufficiently soluble in
the chosen organic solvent that the reaction mixture is a
homogenous solution at either the outset of the reaction or becomes
a homogenous solution over the course of the reaction.
"Substantially soluble" is intended to apply only to the
metal-2,4-dicarbonyl complex and should not be assumed to preclude
those reaction mixtures wherein the metallated expanded porphyrin,
once formed, may precipitate out of solution.
Within the scope of the invention is the ability to adjust the
solubility of the metal-2,4-dicarbonyl complex and the strength of
the bond(s) between the 2,4-dicarbonyl and the metal ion. The
solubility in organic solvent can be manipulated by varying the
size, charge and hydrophobic/hydrophilic character of the
2,4-dicarbonyl. Similarly, by manipulating the electronic character
of the substituents (i.e. R.sup.21, R.sup.22 and/or R.sup.23) on
the 2,4-dicarbonyl nucleus of Formula III, the strength of the bond
between the 2,4-dicarbonyl and metal ion can be adjusted. For
example, an electron-withdrawing substituent on the 2,4-dicarbonyl
nucleus will reduce the charge concentration on the enolate oxygen
of the 2,4-dicarbonyl resulting in a more weakly bonded
metal-2,4-dicarbonyl complex. The opposite effect is expected from
substituting the nucleus with an electron-releasing substituent.
Thus, by judicious choice of the 2,4-dicarbonyl compound from the
wide array of 2,4-dicarbonyl compounds useful in this invention,
both the solubility and stability of the metal-2,4-dicarbonyl
complex can be adjusted.
The 2,4-dicarbonyl compounds are known compounds that are readily
available worldwide from chemical suppliers. Further, many
2,4-dicarbonyls which are not commercially available are readily
accessible to those of skill in the art by well known synthetic
procedures. For example, see ORGANIC SYNTHESIS: COLLECTED VOLUMES,
Shriner, R. L., et al., Eds., John Wiley and Sons, New York, 1976
(see particularly, Index and more particularly Index at p. 262,
listing 21 diketone syntheses), which is incorporated herein by
reference. Certain preformed metal-2,4-dicarbonyl complexes are
available commercially. For example, metal diketonates are
commercially available. The use of commercially available
metal-2,4-dicarbonyl complexes is also within the scope of the
instant invention. Alternatively, metal-2,4-dicarbonyl complexes
can be prepared by conventional methods known in the art. For
example, general methods for preparing metal-2,4-diketonates are
disclosed in Desreux, J. F., in LANTHANIDE PROBES IN LIFE, CHEMICAL
AND EARTH SCIENCES. THEORY AND PRACTICE. Bunzli, J.-C. G, Ed.,
Elsevier, N.Y., 1989, pp. 43-64, and references therein, which are
incorporated herein by reference.
The metal-2,4-dicarbonyl complex may be prepared in situ in the
expanded porphyrin metallation mixture, or may be prepared separate
from this metallation mixture. For example, when a
metal-2,4-diketonate is utilized, the metal-2,4-diketonate can be
synthesized in bulk, purified and stored until needed. When the
metal-2,4-diketonate is prepared in a solvent which is incompatible
with the expanded porphyrin metallation reaction, the solvent may
be stripped off or otherwise removed or the metal-2,4-diketonate
may be precipitated from the reaction mixture by addition of a
solvent in which the metal-2,4-diketonate is insoluble. Thus
synthesized and isolated, the metal-2,4-diketonate is subsequently
redissolved into the reaction medium for the metallation of the
expanded porphyrin. In preferred embodiments, the
metal-2,4-dicarbonyl complex is formed in situ by combining the
metal salt and the 2,4-dicarbonyl in the solvent intended for the
metallation reaction. After an incubation period, the expanded
porphyrin is added directly to the solution of the
metal-2,4-dicarbonyl complex.
The starting salt used as the source of the metal ion can be any
salt that dissociates sufficiently in the presence of the
2,4-dicarbonyl to allow a complex between the metal ion and the
2,4-dicarbonyl to be formed. In preferred embodiments, the metal
salt is a metal acetate, chloride, nitrate, oxide or sulfate. In
further preferred embodiments the metal salts are lanthanide ion
salts. In a particularly preferred embodiment, the metal salt is
lutetium(III) acetate or gadolinium(III) acetate.
A variety of solvents can be used in the practice of this
invention. The choice of solvent in any particular case will depend
on the solubility of the expanded porphyrin, the metal ion, the
source salt for the metal ion, and the metal-2,4-dicarbonyl
complex. Selection of the solvent will be governed by various
guidelines, including:
(1) The metal-2,4-dicarbonyl complex used is preferably soluble in
the solvent before, during and after treatment with the expanded
porphyrin;
(2) The unmetallated 2,4-dicarbonyl compound is preferably
appreciably soluble following transfer of the metal ion to the
expanded porphyrin;
(3) The unmetallated expanded porphyrin preferably is appreciably
soluble in the selected solvent; and
(4) The solvent does not displace the 2,4-dicarbonyl of the
intermediate metal-2,4-dicarbonyl complex to form a different
complex which is unreactive with the expanded porphyrin.
The solvents will, in general, be polar solvents. For example
alcohols, esters, ethers, amides, sulfoxides and ketones can be
used in practicing the instant invention. Specific examples include
methanol, ethanol, isopropanol, n-butanol, dimethyl sulfoxide,
dimethyl formamide, tetrahydrofuran, acetone, ethylene glycol
dimethyl ether, dioxane and mixtures of such solvents with each
other and/or water. In preferred embodiments, the expanded
porphyrin is a texaphyrin or a texaphyrin precursor and the solvent
is an alcohol, with short chain alcohols such as C.sub.1 -C.sub.4
alcohols being preferred. Particularly preferred are methanol and
ethanol.
Sufficient 2,4-dicarbonyl compound is used to consume all or
substantially all of the noncomplexed metal ion. In preferred
embodiments, approximately one equivalent of the 2,4-dicarbonyl
compound will be sufficient to rapidly convert the metal ion into
the corresponding metal-2,4-dicarbonyl complex. In embodiments
wherein the metal ion is supplied as a salt that is only partially
soluble in the reaction medium, an excess of the 2,4-dicarbonyl
compound can be used to encourage solubilization of the metal ion.
The unreacted 2,4-dicarbonyl compound can be allowed to remain in
the reaction mixture or it can be removed from the
metal-2,4-dicarbonyl complex prior to reacting the
metal-2,4-dicarbonyl complex with the expanded porphyrin.
In preferred embodiments, the molar ratio of 2,4-dicarbonyl
compound to metal ion will be from about 3.5:1.0 to about 0.1:1.0,
and most preferably in the range of from about 1.5:1.0 to about
0.5:1.0.
The amount of metal-2,4-dicarbonyl complex that is used to react
with the expanded porphyrin and to form the metallated expanded
porphyrin can vary depending on the metal ion chosen, the expanded
porphyrin, the concentrations of these components in the reaction
mixture, and the reaction conditions. In most cases, however, best
results will be achieved with a metal-2,4-dicarbonyl
complex-to-expanded porphyrin molar ratio of from about 1.0:1.0 to
about 3.0:1.0 and preferably from about 1.0:1.0 to about
1.5:1.0.
When conducted in organic solvents, the reaction between the
metal-2,4-dicarbonyl complex and the expanded porphyrin can be
performed under neutral or basic conditions. Basic conditions are
most preferred when the expanded porphyrin contains ionizable
groups which are involved in the complexation. Thus, bases which
are soluble in the reaction medium (e.g. R.sub.3 N, R.sub.2 NH,
RNH.sub.2, etc.) may be added to ensure that the complexing groups
remain unprotonated. Alternatively, bases which are substantially
insoluble in the reaction mixture (e.g., K.sub.2 CO.sub.3,
BaCO.sub.3) may be used.
Metallation of the expanded porphyrin can be conducted at any
temperature between the boiling and freezing points of the reaction
medium. The criteria used in choosing the reaction temperature will
be the rate of expanded porphyrin metallation and the stability of
the products and reactants at the chosen temperature. The preferred
temperature is one that maximizes the rate of product formation
while minimizing any decomposition of either products or reactants.
Similar considerations apply to the reaction in which the
metal-2,4-dicarbonyl complex is formed. Adequate results are
generally obtained at temperatures which are between about
20.degree. C. and about 80.degree. C. In preferred embodiments
wherein the reaction solvent is an alcohol, the expanded porphyrin
metallation and formation of the metal-2,4-dicarbonyl complex
reactions are run at the reflux temperature of the reaction
solvent.
The reaction is permitted to continue for a period of time
sufficient to allow transfer of the metal ion from the
metal-2,4-dicarbonyl complex to the expanded porphyrin. The
reaction can be assisted by agitation. In most cases, the reaction
will be completed within fifteen hours, and reaction times of about
six to about eight hours are preferred. In preferred embodiments
utilizing texaphyrin precursors, the precursor is oxidized to a
texaphyrin contemporaneous with the metallation reaction. Oxidation
is effected by the use of molecular oxygen or chemical oxidizing
agents. In preferred embodiments, molecular oxygen is bubbled into
the reaction mixture during the metallation.
Isolation and purification of the desired product is achieved by
conventional means such as, for example, evaporation, extraction,
precipitation, crystallization, filtration, decantation,
centrifugation, chromatography or a combination of such techniques.
In embodiments wherein the metallated expanded porphyrin remains
dissolved in the reaction medium, it can first be recovered by
evaporation of the solvent or other conventional means. In
preferred embodiments a solvent is available in which the
2,4-dicarbonyl and metal-2,4-dicarbonyl complex are soluble, yet in
which the metal-expanded porphyrin is insoluble.
The following detailed examples are offered for illustrative
purposes only.
EXAMPLES
Materials and Methods
The following materials and methods were used in each of the
examples detailed below.
Materials
Lu(OAc).sub.3.xH.sub.2 O was obtained from Strem Chemicals,
Newburyport, Mass., USA. Triethylamine, Arsenazo III and
2,4-pentanedione were obtained from Aldrich Chemical Company, St.
Louis, Mo., USA. Methanol was obtained from J. T. Baker,
Phillipsburg, N.J., USA and 4% N.sub.2 /96% O.sub.2 was obtained
from Air Liquide, Walnut Creek, Calif., USA. Reverse phase TLC
plates (KC8F, 1.5.times.10 cm) were obtained from Whatman, Inc.,
Clifton, N.J., USA. LZY-54 zeolite was obtained from UOP Molecular
Sieve Plant, Chickasaw, Ala., USA.
Methods
1. Lu (III)-expanded porphyin purity by HPLC
The purity of the expanded porphyrin was assessed using
reverse-phase HPLC on a Prodigy ODS2 column. The column was
150.times.3.2 mm in size with a 5 .mu. particle size. The mobile
phase was 72:28 100 mM ammonium acetate (pH 4.3):acetonitrile. The
flow rate was 0.7 mL/min and the column effluent was monitored at
470 nm. The total run time was 28 min. Under these conditions, the
Lu(III)-expanded porphyrin had a retention time of approximately 22
minutes.
2. Monitoring the course of the metallation reaction
The reaction was monitored for completeness using UV/vis
spectroscopy. Briefly, an aliquot (one drop) of the reaction
mixture was withdrawn, diluted with MeOH (4 mL) and the UV/vis
spectrum was measured from 325-900 nm. The concentration of the
UV/vis sample was adjusted with MeOH if necessary to maintain the
maximum absorbance between 1.5 and 2.0. Glacial acetic acid (1
drop) was added to the cuvette, the mixture was agitated and the
spectrum was measured as described above. When the ratio of the
absorbance at 354 nm to that at 475 nm reached 0.24-0.26 the
reaction was deemed to be complete.
3. Detecting the presence of uncomplexed metal ion
The presence of uncomplexed metal ion in the reaction mixture was
assayed using reverse-phase thin layer chromatography (TLC). A
sample of the reaction mixture was spotted onto a C.sub.8
-reverse-phase TLC plate and the plate was developed in 9:1
MeOH:acetic acid. After removal from the developing solvent, the
plate was dried. The green-colored metallated expanded porphyrin
migrated with the solvent front. The lower one-fourth of the plate
is stained with a MeOH solution of Arsenazo III (0.4 mg/mL). A blue
spot observed at the origin is indicative of free metal ion.
3. Elemental analysis
Elemental analyses (C, H, N, Lu.sup.+3) were obtained from
Schwarzkopf Microanalytical Laboratory, Woodside, N.Y., U.S.A.
Example 1
This example illustrates the prior art method for preparing a
lutetium-texaphyrin complex from an sp.sup.3 expanded porphyrin and
lutetium acetate hydrate. The metallation is performed in MeOH and
utilizes Lu(III) acetate as a Lu(III) source. Due to the low
solubility of the metal salt in organic solvents, an excess of both
the Lu(III) acetate and also of MeOH is required to achieve a
satisfactory concentration of Lu(III) in solution. This reaction is
characterized by lengthy reaction times (29 h) and it affords the
final product in rather low yields (27%). The starting sp.sup.3
expanded porphyrin is a texaphyrin precursor represented by Formula
IV and the complex is represented by Formula V. ##STR4##
In a dry 3 L three-neck round-bottom flask, the expanded porphyrin
(IV) (50 g, 55 mmol) was dissolved in MeOH (1500 mL). To this
well-stirred, dark red solution was added lutetium (III) acetate
(35.0 g, 82.1 mmol) and triethylamine (76 mL, 1 mole). The
resulting suspension was heated to reflux. After 2 h at reflux, air
was bubbled for 30 min into the suspension via a gas dispersion
tube (flow rate=50 mL/min). During the next 27 hours, the
suspension was maintained at reflux and air was intermittently
bubbled through the mixture at a flow rate of 60 mL/min. The total
time over which the air was introduced into the mixture was
approximately 4 h. After 29 h, the reaction was deemed complete.
The suspension was cooled to room temperature, filtered through a
pad of CELITE.RTM. 545 and the solvent was removed under reduced
pressure. The remaining dark-green solid was suspended in acetone
(1600 mL) and stirred for 1 h at room temperature. The green solid
was collected by filtration, washed with acetone (1000 mL) and
dried in vacuo for several hours, yielding 38 g of crude
Lu(III)-macrocycle. The crude Lu(III)-macrocycle was dissolved in
MeOH (1400 mL) and this solution was stirred for 30 min. then
filtered through a pad of CELITE.RTM. 545. Water (140 mL) and
acetic acid washed LZY-54 zeolite (150 g) were added to the
solution and the mixture was stirred by means of an overhead
stirring apparatus for approximately 5 h. The zeolite was removed
by filtration through Whatman #3 filter paper and rinsed with MeOH
(200 mL). The filtrate and rinses were combined and concentrated to
approximately 900 mL. This solution was passed through a column of
AMBERLITE.RTM. IRA-904 anion exchange resin (acetate form, 2.0
cm.times.18 cm, 10-12 mL flow rate). The column was rinsed with
MeOH (300 ml) and the rinse solution and eluent were combined and
evaporated to dryness under reduced pressure. The resulting solid
was suspended in acetone (600 mL), stirred 2 h, collected by
filtration and washed with acetone (100 mL). The crude product was
suspended in ethanol (650 mL) and the mixture was heated to reflux
for 1 h. Once homogenous, the green solution was hot-filtered. The
filtrate was allowed to cool slowly to room temperature, then
placed in a freezer overnight to ensure complete crystallization.
The crystallization mixture was stirred for 1 h at room temperature
and the crystalline Lu(II)-texaphyrin was collected by filtration.
The collected Lu(III)-texaphyrin was dried in vacuo for 24 h at
room temperature and subsequently for 48 h at 45.degree. C. to
afford 17 g (27%) of the pure metallated Lu(III)-texaphyrin (V) as
a dark green solid.
The metallated Lu(III)-texaphyrin (V) was analyzed by UV/vis
spectroscopy, fast atom bombardment mass spectrometry (FAB MS),
high resolution mass spectrometry (HRMS) and elemental analysis
giving the following results:
UV/vis (MeOH) .lambda.max (nm), (log e): 354 (4.33), 414 (4.67),
474 (5.10), 672 (sh), 732 (4.62).
FAB MS: [M-OAc.sup.- ].sup.+ : m/e 1106.4
HRMS: [M-OAc.sup.- ].sup.+ : m/e 1106.4330 (calc'd. for [C.sub.48
H.sub.66 N.sub.5 O.sub.10 Lu(OAc)].sup.+, 1106.4351).
______________________________________ Elemental Analysis [C.sub.48
H.sub.66 N.sub.5 O.sub.10 Lu](OAc)2H.sub.2 O Calculated Found
______________________________________ C 52.74 52.74 H 6.30 6.18 N
5.91 5.84 ______________________________________
As can be seen from the above-detailed example, the prior art
methods for metallating expanded porphyrins with lanthanide salts,
particularly those of lutetium (III), in organic solvents require
long reaction times and provide rather low yields. These results
are thought to derive from the low solubility of the metal salt in
the organic solvent. In the examples below are detailed the methods
of the instant invention wherein using a metal complex which is
soluble in an organic solvent provides advances over the prior art
method; notably, the use of shortened reaction times and a two-fold
increase in the yield of the desired product.
Example 2
This example demonstrates an embodiment of the invention in which
the complex between 2,4-pentanedione and lutetium (III) is
preformed in MeOH and subsequently combined with macrocycle (IV),
an expanded porphyrin. The Lu(III) 2,4-pentanedione complex
comprises a source of Lu(III) which is markedly more soluble in
organic solvents than the precursor Lu(III) acetate. The solubility
of the Lu(III) complex allows the reaction to be performed using
only one equivalent of the Lu(III) source, yet affords a 2-fold
increase in the yield (52% vs. 27%) of the Lu(III)-texaphyrin
(V).
Lu(OAc).sub.3.xH.sub.2 O (1.856 g, 4.38 mmol), 2,4-pentanedione
(0.449 mL, 4.37 mmol) and triethylamine (4.80 mL, 34.44 mmol) were
combined in MeOH (40 mL). Macrocycle (IV) (4.008 g, 4.38 mmol) in
MeOH (10 mL) was added and the solution was heated at reflux for 22
hours. 4% O.sub.2 /96% N.sub.2, used as an oxidant, was sparged
through the reaction mixture at a flow rate of approximately 16
mL/min for a total of 8 hours.
The reaction was allowed to cool to room temperature and the
solvent was then removed under reduced pressure. The resulting
residue was slurried in acetone (33 mL) and stirred for 1 h. The
Lu(III)-texaphyrin (V) was collected by filtration and washed with
acetone until the filtrate was practically colorless. The
Lu(III)-texaphyrin was dissolved in MeOH (91 mL) and the solution
was agitated on a rotary evaporator. Water (9 mL) and acetic acid
washed zeolite (2.0 g) were added to the solution. Agitation was
continued for 1 h. The zeolite was removed by filtration through #3
Whatman filter paper. Another portion of zeolite (2 g) was added to
the filtrate and the mixture was agitated for 2 h and filtered. The
filtrate was passed down a column of AMBERSEP.RTM. 900 anion
exchange resin (acetate form; 1.5 cm.times.14 cm). The column was
washed with approximately 1 bed volume of MeOH. The main eluent and
wash solutions were combined and the volume was reduced by
one-third under reduced pressure. The remaining MeOH solution was
filtered through a 0.1 .mu. nylon filter. The filtered solution was
evaporated to dryness under reduced pressure (a small amount of
EtOH was added to form an azeotrope with any remaining H.sub.2 O)
and the resulting residue was dried under high vacuum overnight
affording 2.961 grams of the crude Lu(III)-texaphyrin.
The crude Lu(III)-texaphyrin (2.961 g) was dissolved in a mixture
of ethanol (45 mL) and H.sub.2 O (0.45 mL) by refluxing under
N.sub.2 on an oil bath. After 1 h, the temperature of the solution
was slowly reduced by ramping down the temperature of the oil bath
to 30.degree. C. in 10.degree. C. increments over 7 h. After
removing the oil bath, the mixture was allowed to stand at room
temperature for 1 h, then cooled to 10.degree. C. for 1 h. The
crystals which formed were collected by filtration, washed with
isopropyl alcohol and then acetone (20 mL). The recrystallized
Lu(III)-texaphyrin was dried in vacuo (10 torr) overnight affording
2.673 g (52%) of the pure Lu(III)-texaphyrin (V).
The purity of the Lu(III)-texaphyrin was confirmed by HPLC and
elemental analysis. The HPLC analysis demonstrated that the
crystalline material was approximately 93 % pure. The elemental
analysis of the product corresponded with the calculated values for
the Lu(III)-texaphyrin (V).
______________________________________ Elemental Analysis [C.sub.48
H.sub.66 N.sub.5 O.sub.10 Lu](OAc)2H.sub.2 O Calculated Found
(Dried in vacuo) ______________________________________ C 53.56
53.02 53.00 H 6.22 6.32 6.17 N 6.01 6.04 6.10 Lu 15.00 15.11
______________________________________
Example 3
This example illustrates that use of the Lu(III) 2,4-pentanedione
complex in a dilute reaction mixture provides a 2-fold increase in
the yield of a product which is purer than that obtained by the
method outlined in Example 1. This example further shows that the
Lu(III) 2,4-pentanedione complex provides a useful Lu(III) ion
source even when highly diluted. The increased dilution of the
Lu(III) source does not require correspondingly increased reaction
times to achieve a high yield of the pure metallated
Lu(III)-texaphyrin.
Lu(OAc).sub.3 -xH.sub.2 O (0.55 g, 1.30 mmol), 2,4-pentanedione
(0.133 mL, 1.30 mmol) and triethylamine (1.2 mL, 8.61 mmol) were
combined in MeOH (55 mL). The mixture was stirred until the
lutetium salt was completely dissolved. Macrocycle (IV) (1.00 g,
1.09 mmol) was added and the solution was heated at reflux, under a
4% O.sup.2 /96% N.sub.2 atmosphere for 22 h.
The reaction was allowed to cool to room temperature and the
solvent was then removed under reduced pressure. The resulting
residue was slurried in acetone (20 mL) and stirred for 30 min. The
Lu(III)-texaphyrin was collected by filtration and washed with
acetone until the filtrate was practically colorless. The
Lu(III)-texaphyrin was dissolved in MeOH (29 mL). Water (2.9 mL)
and acetic acid washed zeolite (3.0 g) were added to the solution
and the mixture was agitated on a rotary evaporator for 1 h. The
zeolite was removed by filtration through #3 Whatman filter paper
and the collected zeolite was washed with MeOH. The filtrate and
wash were combined and the solution was again treated with acetic
acid washed zeolite, agitated for 7 h and filtered. The filtrate
was passed down a column of AMBERSEP.RTM. 900 anion exchange resin
(acetate form; 1.5 cm.times.15 cm). The column was washed with
approximately 1-2 bed volumes of MeOH. The main eluent and wash
solutions were combined and evaporated to dryness under reduced
pressure. The residue was redissolved into a minimum amount of MeOH
and the solution was filtered through a 0.2 .mu. teflon syringe
filter. The filtered solution was evaporated to dryness under
reduced pressure and the resulting residue was dried under high
vacuum for 10 h affording 0.8996 g of the crude
Lu(III)-texaphyrin.
The crude Lu(III)-texaphyrin (0.8996 g) was dissolved in a mixture
of ethanol (14 mL) and H.sub.2 O (0.14 mL) by refluxing under
N.sub.2 for approximately 1 h. The resulting solution was allowed
to cool slowly to room temperature during which time crystals of
the Lu(III)-texaphyrin separated from the solution. The crystals
were collected by filtration, washed with isopropyl alcohol and
then acetone. The recrystallized Lu(III)-texaphyrin was dried under
vacuum (10 torr) overnight affording 0.734 g (58%) of the pure
metallated Lu(III)-texaphyrin (V).
The purity of the Lu(III)-texaphyrin was confirmed by HPLC and
elemental analysis. HPLC analysis demonstrated that the crystalline
material was approximately 92.24% pure. The elemental analysis
corresponded to the values calculated for the Lu(III)-texaphyrin
(V).
______________________________________ Elemental Analysis [C.sub.48
H.sub.66 N.sub.5 O.sub.10 Lu](OAc)2H.sub.2 O Calculated Found
(Dried in vacuo) ______________________________________ C 53.56
52.75 52.49 H 6.22 6.71 6.87 N 6.01 5.88 6.14 Lu 15.00 15.05 Cl
<0.1 ______________________________________
Example 3 demonstrates that the Lu(III) 2,4-pentanedione complex
provides a useful source of the Lu(III) ion even when present in
the reaction mixture at fairly low concentrations. Even at low
concentrations of the soluble Lu(III) source, increased reaction
times are not necessary to achieve higher yields than are afforded
by the prior art method.
Example 4
This example illustrates the utility of the Lu(III)
2,4-pentanedione complex at concentrations which are intermediate
to those described in Examples 2 and 3. In the present example, the
concentration of the Lu(III) complex is approximately one-half that
of the concentration in Example 2 and 2-fold greater than the
concentration in Example 3. Similar to the results obtained in the
above examples, use of approximately one equivalent of this Lu(III)
source provides a higher yield of a pure metallated
Lu(III)-texaphyrin than is obtained using the prior art method.
Lu(OAc).sub.3.xH.sub.2 O (0.927 g, 2.19 mmol), 2,4-pentanedione
(0.225 mL, 2.19 mmol) and triethylamine (2.40 mL, 17.22 mmol) were
combined in MeOH (50 mL). The mixture was stirred until the
lutetium salt was completely dissolved. Macrocycle (IV) (1.99 g,
2.18 mmol) was added and the solution was heated at reflux, under a
4% O.sub.2 /96% N.sub.2 atmosphere for 18 h.
The reaction was allowed to cool to room temperature and the
solvent was then removed under reduced pressure. The resulting
residue was slurried in acetone (20 mL) and stirred for 30 min. The
Lu(III)-texaphyrin was collected by filtration and washed with
acetone until the filtrate was practically colorless. The expanded
porphyrin was dissolved in MeOH (50 mL) and H.sub.2 O (5 mL).
Acetic acid-washed zeolite (4.0 g) was added to the solution and
the mixture was agitated on a rotary evaporator for 30 min. The
zeolite was removed by filtration through #3 Whatman filter paper
and the collected zeolite was washed with MeOH. The filtrate and
wash were combined and the solution was again treated with acetic
acid washed zeolite (4.0 g), agitated for 30 minutes and filtered.
The filtrate was passed down a column of AMBERSEP.RTM. 900 anion
exchange resin (acetate form; 1.5 cm.times.14 cm). The column was
washed with approximately 1 bed volume of MeOH. The main eluent and
wash solutions were combined and evaporated to dryness under
reduced pressure and the resulting residue was dried in vacuo
overnight affording 1.738 grams of the crude
Lu(III)-texaphyrin.
The crude Lu(II)-texaphyrin (1.738 g) was dissolved in ethanol (26
mL) and water (0.260 mL) by refluxing under N.sub.2. The resulting
solution was allowed to cool slowly to room temperature during
which time crystals of the Lu(III)-texaphyrin separated from the
solution. The crystals were collected by filtration, washed with
isopropyl alcohol and dried under vacuum (10 torr) overnight
affording 1.59 g (63%) of the pure Lu(III)-texaphrin (V).
The purity of the Lu(III)-expanded porphyrin was confirmed by HPLC
and elemental analysis. HPLC analysis demonstrated that the
crystalline material was approximately 93% pure. The elemental
analysis corresponded to the values calculated for the
Lu(III)-texaphyrin.
______________________________________ Elemental Analysis [C.sub.48
H.sub.66 N.sub.5 O.sub.10 Lu](OAc)2H.sub.2 O Calculated Found
(Dried in vacuo) ______________________________________ C 53.56
52.96 53.01 H 6.22 6.34 6.42 N 6.01 5.82 6.04 Lu 15.00 15.04
______________________________________
Similar to Examples 2 and 3 above, Example 4 demonstrates that the
Lu(III) 2,4-pentanedione complex provides a useful source of the
Lu(III) ion which is soluble in organic solvents.
Example 5
Similar to Example 4, this example illustrates the usefulness of
the Lu(III) 2,4-pentanedione complex at concentrations which are
intermediate to those described in Examples 2 and 3. Use of this
intermediate concentration provides a high yield of a pure final
product and serves to further establish that the organic-soluble
Lu(III) source of the invention is useful over a range of
concentrations.
Lu(OAc).sub.3.xH.sub.2 O (1.393 g, 3.28 mmol), 2,4-pentanedione
(0.337 mL, 3.28 mmol) and triethylamine (3.60 mL, 25.83 mmol) were
combined in MeOH (45 mL). Macrocycle (IV) (3.00 g, 3.28 mmol) and
MeOH (5 mL) were added and the solution was heated at reflux, under
a 4% O.sub.2 /96% N.sub.2 atmosphere for 12 h.
The reaction was allowed to cool to room temperature and the
solvent was then removed under reduced pressure. The resulting
residue was slurried in acetone (25 mL) and stirred for 1.5 h. The
Lu(III)-texaphyrin was collected by filtration and washed with
acetone until the filtrate was practically colorless. The collected
solid was dried in vacuo affording 2.299 g of the crude metallated
Lu(III)-texaphyrin. To the Lu(III)-texaphyrin was added MeOH (66
mL) and the resulting mixture was agitated on a rotary evaporator.
H.sub.2 O (6.6 mL) was added and the agitation was continued until
the Lu(III)-texaphyrin was largely dissolved. Acetic acid washed
zeolite (4.0 g) was added to the solution and the mixture was
agitated for 1.5 h. The zeolite was removed by filtration through
#3 Whatman filter paper and the collected zeolite was washed with
MeOH. The filtrate and wash were combined and the solution was
again treated with acetic acid washed zeolite (4.0 g), agitated for
1 h and filtered. The filtrate was passed down a column of
AMBERSEP.RTM. 900 anion exchange resin (acetate form; 1.5
cm.times.13 cm). The column was washed with approximately 2 bed
volumes of MeOH. The main eluent and wash solutions were combined
and filtered through a 0.2.mu. nylon filter. The filtrate was
evaporated to dryness under reduced pressure and the resulting
residue was dried in vacuo overnight affording 2.137 grams of the
crude Lu(II)-texaphyrin.
The crude Lu(III)-texaphyrin (2.137 g) was dissolved in ethanol (32
mL) and water (0.32 mL) by refluxing the mixture under N.sub.2 on
an oil bath. The resulting solution was allowed to cool slowly to
room temperature by ramping the temperature of the oil bath down in
10.degree. C. increments. The Lu(III)-texaphyrin began to
crystallize at 60.degree. C. After reaching room temperature, the
mixture was cooled to 10.degree. C. for 30 min. The crystals were
collected by filtration, washed with isopropyl alcohol. The
recrystallized Lu(III)-texaphyrin was dried under vacuum (10 torr)
overnight affording 1.955 g (51%) of the pure Lu(III)-texaphyrin
(V).
The purity of the Lu(III)-texaphyrin was confirmed by HPLC and
elemental analysis. HPLC analysis demonstrated that the crystalline
material was approximately 92-93% pure. The elemental analysis
corresponded to the values calculated for the Lu(III)-texaphyrin
(V).
______________________________________ Elemental Analysis [C.sub.48
H.sub.66 N.sub.5 O.sub.10 Lu](OAc)2H.sub.2 O Calculated Found
(Dried in vacuo) ______________________________________ C 53.56
52.73 53.16 H 6.22 6.34 6.24 N 6.01 6.01 6.12 Lu 15.00 14.92
______________________________________
Similar to Examples 2, 3 and 4 above, Example 5 demonstrates that
the Lu(III) 2,4-pentanedione complex provides a useful source of
the Lu(III) ion which is soluble in organic solvents.
Example 6
In this final example, it is demonstrated that the use of the
intermediate 2,4-diketone complex permits the use of reaction times
which are 3-4-fold shorter than the method of the prior art, while
affording a yield of the desired Lu(III)-texaphyrin which is 2-fold
higher. In addition, the purification of the metallated
Lu(III)-texaphyrin is simplified. Treating the crude product with a
zeolite to remove uncomplexed Lu(III) ions, as in the prior
examples, is eliminated and shown to be unnecessary. The solubility
of the Lu(III)-2,4-pentanedione complex in acetone allows the
Lu(III) which is not bound to the expanded porphyrin to be washed
away from the desired product.
Lu(OAc).sub.3.xH.sub.2 O (0.929 g, 2.19 mmol), 2,4-pentanedione
(0.225 mL, 2.19 mmol) and triethylamine (2.4 mL, 17 mmol) were
combined in MeOH (50 mL). The mixture was stirred until the
lutetium salt was completely dissolved. Macrocycle (IV) (2.00 g,
2.19 mmol) was added and the solution was heated at reflux, under a
4% O.sup.2 /96% N.sub.2 atmosphere for 6 h.
The reaction was allowed to cool to room temperature and the
solvent was then removed under reduced pressure. The resulting
residue was slurried in acetone (25 mL) and stirred for 1 h. The
Lu(III)-texaphyrin was collected by filtration and washed with
acetone until the filtrate was practically colorless. The
Lu(III)-texaphyrin was dissolved in MeOH (50 mL) and was passed
down a column of AMBERSEP.RTM. 900 anion exchange resin (acetate
form; 1.5 cm.times.17 cm). The column was washed with approximately
1 bed volume of MeOH. The main eluent and wash solutions were
combined and the solution was filtered through a 0.2.mu. nylon
filter. The filtered solution was evaporated to dryness under
reduced pressure and the resulting residue was dried in vacuo
overnight affording 1.719 g of the crude Lu(III)-texaphyrin.
The crude Lu(III)-texaphyrin (1.719 g) was dissolved in ethanol (26
mL) and H.sub.2 O (0.26 mL) by refluxing under N.sub.2 . After 2 h
at reflux EtOH (2 mL) and H.sub.2 O (0.020 mL) were added. The
resulting solution was allowed to cool slowly to room temperature
during which time crystals of the Lu(III)-texaphyrin separated from
the solution. The crystals were collected by filtration, washed
with isopropyl alcohol and dried under vacuum (10 torr) for several
hours affording 1.50 g (62%) of the pure Lu(III)-texaphyrin
(V).
Example 6 demonstrates that the Lu(III) 2,4-pentanedione complex
provides a useful source of the Lu(III) ion which is soluble in
organic solvents. Further, this solubility can be exploited to both
reduce the reaction time for metallation and to simplify the
purification of the metallated Lu(III)-texaphyrin.
Taken together, the examples detailed above demonstrate that the
method of the invention provides a metal ion source having a
solubility in organic solvents which is significantly enhanced
relative to the solubility of the simple metal salts of the prior
art. The enhanced solubility allows the reaction to be run at a
higher reactant concentration which in turn decreases the overall
reaction time necessary to effect a satisfactory conversion of the
reactants to the desired metallated texaphyrin. Additionally,
similarly high yields are obtained even when the metal source is
dilute. The dilute nature of the metal source does not necessitate
increased reaction time. In addition, the examples demonstrate that
the instant invention is operable over a range of reactant
concentrations and also affords the metallated texaphyrin in yields
which are approximately two-fold greater than that obtained using
the prior art method. Furthermore, it has been demonstrated that
the use of an organic-soluble metal ion source simplifies the
purification protocol.
The foregoing is offered primarily for purposes of illustration. It
will be readily apparent to those skilled in the art that the
materials, proportions, procedural steps and other parameters of
the formulation and its use may be further modified or substituted
in various ways without departing from the spirit and scope of the
invention.
* * * * *